Disease predispositions in dogs and cats: the fuller story

摘要

Companion animals are often bred according to the whims and needs of mankind rather than following the harsh survival rules of natural selection. It is widely accepted that almost all dog and cat breeds have specific diseases to which they are particularly prone (ie. predisposed). Consequently, breed-related disease has become an important anthropogenic-welfare issue and it behoves everyone with an interest in companion animals to strive to reduce these welfare costs.Domestic dogs and cats have become integral parts of modern human family life. Dog and cat populations in the UK are each estimated at around eight to 10 million animals (Murray et al, 2010; Asher et al, 2011; PFMA, 2012), with 24-31% of UK households estimated to own at least one dog (Asher et al, 2011; Murray et al, 2010). Humans have expressed their 'love' of these species by selecting for specific favoured characteristics that have led to over 400 unique dog breeds and 70 cat breeds. In the UK, 80%of dogs and 10% of cats are now purebreds (O'Neill et al, 2014b; O'Neill et al, 2014a). The benefits of dog and cat ownership are well known, and include both physical (Ownby et al, 2002; Friedmann and Son, 2009) and psychological gains (Virues-Ortega and Buela-Casal, 2006; Walsh, 2009). However, man has progressively played with the shape of the modern dog such that the dog is now the most phenotypically diverse mammal at a species level (Wayne et al, 2006) and it is increasingly questioned whether modern-breed selection towards extremes of conformation have allowed dog health and welfare to derive comparable benefits (McGreevy and Nicholas, 1999; Rooney, 2009). Each of the 50 most popular breeds in the UK has at least one reported conformational predisposition to disease (Asheret al, 2009) and almost 400 non-conformational inherited disorders have been identified (Summers et al, 2010). The debate over the health impacts from man's manipulation with dog breeds came to a head in 2008 when the BBC aired a documentary called Pedigree Dogs Exposed that claimed purebred dog health was deteriorating to an unacceptable level because of man's desire for the 'perfect' dog (BBC, 2008). Three major reports followed that all concurred that pedigree-breeding practices did impose welfare costs on dogs but, more crucially, concluded that critical data gaps existed on disorder prevalence and that these gaps were constraining effective reforms (Bateson, 2010, Rooney and Sargan, 2008; APGAW, 2009). At that time, prevalence data had been published on only 1 % of inherited disorders affecting popular UK dog breeds (Collins et al, 2011). Essentially, 'believing' that a problem exists and having 'evidence' for what that problem may be, are two very different things; and optimal progress to resolve any issue should be based on evidence rather than opinion.